Inflatable seals

ABSTRACT

An inflatable seal system in a tool having opposed parts which are relatively moveable together with the inflatable seal system therebetween. The inflatable seal system comprising a longitudinally extending seal cavity and a seal extending longitudinally along the seal cavity. The seal comprises an inflatable portion and an abutment portion for sealingly abutting against an opposing surface, wherein the inflatable portion remains in the seal cavity when the seal is deflated.

This invention relates to inflatable seals and in particular, but notexclusively, to inflatable seals in the field of the manufacture ofinterior panels for motor vehicles.

Certain types of interior panels for motor vehicles consist of asubstrate (of e.g. glass reinforced urethane, fibre board or the like),a layer of foam, and then a skin (of e.g. PVC). In order to fabricatesuch panels the skin is placed in a cavity formed in the lower part of atool. In one method, known as an `open pour mould`, liquid foam is thenpoured onto the skin and the substrate, which is supported by the upperpart of the tool, is brought down to within a predetermined distance ofthe skin. An exothermic chemical reaction causes the foam to expand,filling the volume between the substrate and the skin. Alternatively,the foam could be injected between the skin and the substrate after thetool has been closed.

A seal is required between the upper and lower parts of the tool toprevent escape of the foam from around the periphery of the tool. Afterthe foam has expanded, one technique involves lifting the upper toolinitially by a small amount to release pressure slowly without fullyopening the tool. However, the foam can then undergo further expansion,distorting the shape of the finished panel. It is therefore generallypreferred to use an inflatable seal since this can be deflated slightlyto allow the built-up pressure to be released without having to open thetool.

Thus in a known tool for producing vehicle interior panels, aninflatable seal is disposed around the periphery of one of the toolparts, usually the lower part. In multiple production runs it isnecessary to clean excess dried foam that has been deposited by aprevious operation from the edge of the tool part, in the region nearthe seal. This is done with sharp implements such as knives andscrapers. Whilst doing this the person scraping the tool mayinadvertently cut or nick the seal, thereby causing it to leak wheninflated. Not only does this cause considerable delay whilst the seal isreplaced, but the leak may not be noticed until after the foam has beenpoured and the tool parts brought together, potentially causing defectsin the panel which then has to be discarded.

In an attempt to solve this problem, it is possible to use a sealreinforced by fibres running along the length of the seal. Whilst thisdoes go some way to alleviating the problem, it has the drawback ofreducing the flexibility of the seal, thereby restricting its usefulnessfor applications in vehicle interior panel production where it is oftennecessary to incorporate relatively tight curves in the path of theseal.

According to one aspect of the present invention, there is provided aninflatable seal system in a tool having opposed parts which arerelatively movable together with the inflatable seal systemtherebetween, the inflatable seal system comprising a longitudinallyextending seal cavity and a seal extending longitudinally along the sealcavity, said seal comprising an inflatable portion and an abutmentportion for sealingly abutting against an opposing surface, wherein theinflatable portion remains in the seal cavity when the seal is deflated.

With such an arrangement, when the seal is deflated, the inflatableportion of the seal is protected from damage, for example from scrapingimplements, by virtue of it remaining in the seal cavity.

The abutment portion may be formed so as to be relatively thick in theradial direction when compared to the inflatable portion and also solidso that, even if the abutment portion projects from the seal cavity whenthe seal is deflated, any damage caused by scraping or cleaningimplements will not cause the inflatable seal to leak. The arrangementis preferably such that only the abutment portion is exposed to theoutside when the seal is deflated.

Because the inflatable portion of the seal is protected by the sealcavity, the seal can be made to be relatively deformable, so that it canreadily follow arcuate portions of the seal cavity, even quite sharplycurved portions if required. It is thus not necessary to mould the sealspecially to fit the arcuate portions of a particular cavity. Sucharcuate portions may be arcuate in the lateral direction, the upwarddirection (so as to be "convex") or the downward direction (so as to be"concave"). It will be appreciated that references to "upward" or"downward" herein are used for the purposes of explanation and on thebasis that the seal cavity has a "bottom" and a "top", but should not beunderstood as limiting the orientation in which the inflatable sealsystem may be used. Thus the top of the seal cavity may face upwardly,downwardly, sideways etc.

The seal is preferably not reinforced by a second material. Thus theseal may be relatively deformable and easy and inexpensive tomanufacture, as compared to e.g. fibre-reinforced rubber.

Preferably the inflatable seal is an extrusion. Again, this allows it tobe easy and inexpensive to manufacture.

The seal cavity may be formed of parts which can be opened up to allowlocation of the seal, but preferably the seal cavity is of fixed shape.For example, the seal cavity may be defined in a body of mouldedmaterial e.g. moulded resin.

Although the seal may be axially insertable along the seal cavity, thearrangement is preferably such that the seal is inflatable into the sealcavity through the top thereof. This will greatly facilitate location ofthe seal and is advantageous in situations where the seal has to beperiodically replaced. In order to allow for such insertion, theabutment portion preferably has a width narrower than that of the sealcavity.

It is preferred for the inflatable portion of the seal to remain in theseal cavity when the seal is inflated. This provides further protectionfor the inflatable portion. In a preferred arrangement, the seal cavityhas a main portion in which the inflatable portion of the seal islocated, and has at its top a longitudinally extending slot which has awidth less than that of the main portion and through which the abutmentportion projects when the seal is inflated.

Inevitably small air leaks will sometimes occur from the inflatable sealcausing it to lose effectiveness. If these are not too serious, it ispossible to increase the pressure at which the seal is inflated in orderto compensate. If the inflatable portion of the seal is constrained bythe seal cavity when the seal is inflated, the seal can withstand higherpressures as its tolerance to high pressure is not limited to thesurface strength of the material from which the inflatable seal isfabricated.

The inflatable portion and the abutment portion of the seal may beformed separately of each other. Preferably, however, they are formedintegrally with each other. This again allows the seal to be easy andinexpensive to manufacture, e.g. as an extrusion. In addition, when itis necessary to replace the seal, only one member has to be locatedalong the seal cavity. Thus an integral seal is easier to use than a twopart seal.

In a preferred embodiment the seal further comprises an inwardlyprojecting member such as a tongue or the like projecting into the sealto prevent the abutment portion of the seal fully entering the sealcavity when the seal is deflated. Such a projecting member is ofparticular value when the seal cavity has a concave arcuate portion,i.e. when the path of the cavity is such that the seal must be curvedwith its abutment portion on the inside of the curve. In many situationsa degree of concavity can be accommodated without any problems, but insome circumstances there may be a tendency for the abutment portion toget stuck in the seal cavity, when the seal is deflated, so that itfails to emerge to effect sealing upon inflatable of the seal. Thus theinwardly projecting member may be provided in order to alleviate thisproblem. It can also ensure that the abutment portion remains at the topof the seal cavity when the seal is deflated, so that the inflatableportion is not exposed to the outside and is thus further protected.

One or more inwardly projecting members may be provided, for exampleprojecting laterally inwardly. Preferably, a member projects radiallyinwardly from a wall of the inflatable portion which is substantiallyopposite the abutment portion.

Whilst the seal could be inflated by a suitable liquid, preferably a gasis used to inflate the seal and most preferably compressed air is used.

The seal may be custom made, e.g. moulded, for a particular seal cavity,taking account of its specific curvature(s) along its length. However,this is relatively expensive, particularly when the seal has to beperiodically replaced. It is therefore advantageous to provide a longlength of seal, e.g. stored on a reel, and then to cut an appropriatelength of seal for the seal cavity. Preferably, therefore, the sealextending along the seal cavity has cut ends, and the inflatable sealsystem preferably further comprises a connector for communicating theseal with a source of pressurised fluid at one end of the seal, theother end of the seal being closed to prevent escape of fluid therefrom.

With such a system, new lengths of seal can simply be cut from a storethereof and installed as required. This is not the practice with knowninflatable seal systems which normally have an integrally mouldedfitting for pressurised fluid supply, either in a radial wall or anaxial end wall, and one or more integrally moulded end portions toprevent fluid escape. Such known seals are thus effectively restrictedto being used with a specific seal cavity.

In fact, such an arrangement is inventive in its own right and is ofindependent patentable significance. It may be used in inflatable sealsystems generally, and not only in inflatable seal systems for usebetween opposed tool parts.

Viewed from another aspect therefore, the invention provides aninflatable seal system comprising a longitudinally extending seal cavityand a seal extending longitudinally along the seal cavity, the sealbeing cut to a length appropriate for the seal cavity, a connector forcommunicating the seal with a source of pressurised fluid being providedat one end of the seal, and the other end of the seal being closed toprevent escape of fluid therefrom.

The invention also provides a method of installing an inflatable sealcomprising locating a longitudinally extending seal along alongitudinally extending seal cavity, cutting the seal to an appropriatelength, providing, at one end of the seal, a connector for communicatingthe seal with a source of pressurised fluid, and closing the other endof the seal to prevent escape of fluid therefrom.

A plurality of disposable connectors may be provided, so as to use a newconnector each time a new length of seal is cut for use in the system.Preferably, however, the connector is removable so as to be availablefor reuse with another length of seal.

In a preferred embodiment, the connector is applied substantiallyaxially of the seal, for example having a male portion which fitsaxially into the open end of the inflatable portion. A clamp ispreferably provided around the outside of the seal to hold it againstthe male portion in sealing manner.

The other end of the seal, remote from the connector, may for example beclosed by a simple clamp or the like which compresses the walls of theseal together. Preferably however the other end is closed by a maleportion which fits into the inflatable portion, similarly to theconnector.

The seal may be cut to length either before or after it has been locatedalong the seal cavity. It may be located by axial insertion, butpreferably it is inserted into said seal cavity through a slot in thetop thereof.

It will be appreciated that the above arrangement, involving cuttinglengths of seal from a supply thereof, is well suited to having the sealformed by extrusion. At the seal manufacture stage, no special fittingsor mouldings have to be provided. There may be significant cost savingsover `made to order` seals since long runs may be produced by the sealmanufacture whereas the end user, e.g. the tooling engineer, can simplytake a length of seal `off the shelf` for use in any size or shape ofe.g. tool.

It will be seen by those skilled in the art that the invention alsoextends to a method of making a product using an inflatable seal systemin a tool having opposed parts which are to be relatively movabletogether with the inflatable seal therebetween, wherein the product isdisposed between the opposed tool parts and wherein the inflatable sealsystem is as set out herein.

As mentioned above, the seal cavity may be defined in a body of mouldedmaterial. Viewed from a further aspect the invention provides a methodof making an inflatable seal system in a tool having opposed parts whichare to be relatively movable together with the inflatable sealtherebetween, the method comprising the steps of:

placing a core element along a path on one of the tool parts which is tobe sealed;

moulding a material around the core element;

removing the core element so as to leave a seal cavity, and

locating along the seal cavity an inflatable seal having an abutmentportion and an inflatable portion, such that, when the seal is deflatedsaid inflatable portion remains in the seal cavity.

Certain preferred embodiments of the invention will now be described, byway of example only, with reference to the accompanying drawings inwhich:

FIG. 1 is a cross-sectional view of an inflatable seal in a seal cavity;

FIGS. 2 and 3 are respectively longitudinal and transversecross-sectional views showing how a seal can become stuck in a sealcavity;

FIG. 4 is a cross-sectional view of another embodiment of the inflatableseal having a tongue;

FIG. 5 is a partial cross-sectional view of the lower part of a toolbeing moulded with a seal cavity;

FIG. 6 is a plan view of the lower part of a tool when empty;

FIG. 7 is a front view of a termination assembly for the inflatableseal; and

FIG. 8 is a partial cross-sectional view of a tool for making a vehicleinterior panel before being compressed.

Referring to FIG. 1, an inflatable seal 2 is fitted into a seal cavity 4in a mould 6 which forms the lower part of a tool used to fabricatevehicle interior panels. The seal is preferably made of extruded rubber.The majority of the perimeter of the seal serves as an inflatableportion 8 and is formed of relatively thin rubber i.e. thin enough toflex and allow the seal to expand when it is inflated. In particular twoshoulders 10 are formed to allow the top part of the seal to sag downwhen the seal is in its deflated state. Integrally formed on the toppart of the seal is a generally rectangular solid abutment portion 12.The abutment portion is constrained to slide vertically within avertical slot 14 communicating the cavity 4. As seen from FIG. 1, inthis embodiment the top 16 of the abutment portion lies below the levelof the tool surface 18 in the uninflated state, with the advantage thata scraping implement passed over the tool surface will not contact thetop 16. However the top 16 could alternatively lie flush with or abovethe level of the tool surface 18, because the relatively thickdimensions of the abutment portion 12 enable it to withstand a certainamount of damage from a scraping element without its sealing functionbeing significantly impaired. At the base of the seal is a locating lug20 which may optionally be provided on the seal to fit into acorresponding recess 22 in the seal cavity 4.

When compressed air is passed into the seal, the inflatable portion 8 ispressed outwardly against the walls of the cavity. Where the top part ofthe seal sags down about the shoulders 10, pressure inside the sealforces the rest of inflatable portion 8 to move up into contact with thewalls of the cavity 4, thereby forcing the abutment portion 12 to slideup in the slot 14 so that the top 16 of this portion stands either proudor further proud of the tool surface 18. The extent of vertical movementis designed so that the top 16 of the abutment portion 12 sealing abutsagainst an opposing surface (omitted for clarity) upon inflation of theseal 2. The seal produced between the seal surface 16 and the opposingsurface prevents the escape of foam from the tool. To release thepressure in the tool, the seal may be broken simply by releasing thepressure inside the inflatable seal. This allows the abutment portion 12to fall away from the opposing surface under its own weight, by virtueof the resilience of the seal towards its natural shape or by thepressure of gases which build up in the tool during the foam fillingprocess. It is not however necessary to move the tool surface 18 andopposing surface away from each other, thus preventing irregularitiesoccurring in the foam due to further expansion thereof.

Between foam filling operations, excess foam deposited on the toolsurface 18 must be removed. This is done with a sharp implement such asa knife or the like. Scraping across the surface of the tool surface 18cannot damage the inflatable portion 8, as this remains in the sealcavity 4. Moreover, even if the user of the knife inadvertently puts theblade into the seal cavity the inflatable portion is protected since theonly exposed part is the solid abutment portion 12. The thin walledinflatable portion 8, which would have been punctured by such a slip, isinaccessible.

When used in the fabrication of vehicle interior panels the seal cavity4 will frequently need to follow a longitudinal path which may be curvedin both the vertical and horizontal directions. As may be seen from FIG.2 certain combinations of vertical curves can cause the abutment portion12 of the seal to tend to move so far down from the top 15 of the slot14 that it becomes stuck as shown in FIG. 3 at the point 13 where theslot 14 joins the main body of the cavity 4. In order to prevent thishappening the inflatable seal may be provided with an inwardlyprojecting member in the form of a tongue 30 as may be seen from theembodiment in FIG. 4. When fitting the seal, the tongue 30 prevents thebottom edge 32 of the abutment portion 12 from being pulled too farinside the seal and thus the abutment portion 12 is maintained withinthe entrance passageway 14. The tongue 30 has no material effect on theoperation of the seal when it is inflated.

The production of the cavity 4 in the lower part of the tool will now bedescribed with reference to FIG. 5. Firstly the basic shape of the toolis made. Then a core element 61 is laid around the path which is to besealed. Clearly, if the seal is to have termination assemblies at eachend then it cannot form a continuous loop and so a solid bridging seal62 (see FIG. 6) is provided to join the two ends. Indeed, the path to besealed by the inflatable seal need not follow substantially the wholecontour of the tool, but may instead be in the form of one or more shortsections which are joined by solid seals. Hence a length of core elementis placed along every path element where it is desired to have aninflatable seal. Rein is then poured over the core element and allowedto harden. The core element is pulled out of the tool longitudinallyfrom one end to leave a seal cavity 4. The exact length and path of theseal cavity is not critical since it does not need to match a particularprefabricated seal. Instead, the seal is cut to the right length afterthe cavity has been cast.

The lower tool part 60 will then have an appearance as shown in FIG. 6.The seal cavity 4 in this example extends substantially all the wayround the lower tool part 60 except for a short length of solid bridgingseal 62, in the region of the ends of the seal cavity, where theconnections to a compressed air supply must be made to the seal oncefitted.

To fit the seal, a long length of inflatable seal 2 is taken. The sealis then fitted into the seal cavity 4. For short or relatively straightpaths to be sealed, the seal may be slid longitudinally along the cavityfrom one end, although for more complicated paths, as in this example,it is easier to inset the seal into the cavity from the top by pinchingthe inflatable portion 8 and pushing it through the slot 14 into thecavity 4. Once the seal has been fitted into the cavity it may be cut tothe appropriate length at both ends.

At both ends there is provided a termination assembly as shown in FIG. 7and denoted generally by the numeral 40. The assembly 40 comprises atwo-piece collet 42 which is placed around the seal and a housing body44. The housing body is in two parts 44a and 44b which are boltedtogether by bolts 45. The lower part 44a is fixed to the lower tool part60. A brass air connector 46 is inserted axially into the seal 2 so thatthe cut end of the seal abuts the underside of a collar (not shown)which is formed at the end of the connector. The air connector has asmall air supply hole 48 which communicates with the interior of theseal, and is formed with an internal thread. At one end of the length ofseal the threaded end of a compressed air supply pipe is attached to thethreaded hole 48. At the other end a blanking screw (now shown) isscrewed into the threaded hole 48 to block this end off. The seal 2 isclamped between the air connector 46 and collet 42 by forcing the armsof the collet together by pushing them into a tapered recess 48 in thehousing body 44. This is achieved when housing part 44a is bolted ontohousing part 44b.

The termination assembly may be modified to accommodate seals 2 ofdifferent cross-sectional shapes. For example, in the case of the sealshown in FIG. 4, the connector 46 would have an axially extending recessto receive the tongue 30, and the air supply hole 48 would be laterallyoffset to avoid the tongue 30.

Next (see FIG. 8) a PVC or ABS skin 64 is laid over the lower part ofthe tool 60 and a substrate made from e.g. plastic injection moulding orwood fibre moulding is fitted to the upper part of the tool 68.

The skin is then covered with foam 66, to which a chemical acceleratorhas been added, and which then starts to undergo a chemical reaction andharden. The substrate carried by the upper tool part 68 is brought downto a pre-determined distance away from the lower tool part 60. As thefoam 6 expands and hardens it will be expel gases such as the reactionproducts and also air, from between the tool parts 60. When the foam hasexpanded until it has almost reached the inflatable seal, the seal isinflated. Thus the foam is prevented from escaping, but at the same timethe formation of gas pockets is prevented which could impair the qualityof the finished panel. Once the foam 60 has been allowed to set by apre-determined amount, the seal 2 is deflated again to de-gas the tool.Since the tool parts have not yet been moved apart again at this stage,the panel remains supported and clamped and therefore does not have atendency to bulge. Once the foam has fully hardened and any residual gashas escaped, the tool parts 60,68 may safely be moved apart again. Thesesteps may be automated e.g. by a suitable timed control.

Whilst a method of manufacturing vehicle interior panels using an `openpour` technique has been described, an injection mould technique couldalternatively be used whereby the tool is closed before foam is injectedinto it. Indeed, there may be circumstances in which this method ispreferred since it may not release as may fumes into the workingenvironment as the `open pour` technique.

It will be understood by those skilled in the art that although thepresent invention has been described in terms of a specific embodimentin the context of vehicle interior panel manufacture, appropriateaspects may be applied with equal utility in any application where aninflatable seal is desirable.

I claim:
 1. An inflatable seal system in a tool having opposed partswhich are relatively moveable together with the inflatable seal systemtherebetween, the inflatable seal system comprising a longitudinallyextending seal cavity, said seal cavity having a cavity mouth in theform of a slot, a seal extending longitudinally along the seal cavity,said seal comprising an inflatable portion and an abutment portion forsealingly abutting against an opposing surface, said seal including aninwardly projecting member which projects radially inwardly into theseal from a wall of the inflatable portion which is substantiallyopposite and not connected to said abutment portion by said inwardlyprojecting member to prevent the abutment portion of the seal fullyentering the seal cavity when the seal is deflated wherein the abutmentportion is slidable within said slot and the inflatable portion remainsin the seal cavity when the seal is deflated.
 2. An inflatable sealsystem as claimed in claim 1, wherein the seal and the seal cavity aresuch that during assembly of the inflatable seal system the seal can beinserted into the seal cavity through the top thereof.
 3. An inflatableseal system as claimed in claim 1, wherein the inflatable portion andthe abutment portion are formed integrally with each other.
 4. Aninflatable seal system as claimed in claim 1, wherein the seal is anextrusion.
 5. An inflatable seal system as claimed in claim 1, whereinthe seal is not reinforced by a second material.
 6. An inflatable sealsystem as claimed in claim 1, wherein the seal cavity is defined in abody of moulded material.
 7. An inflatable seal system as claimed inclaim 1, wherein the seal has cut ends, a connector for communicatingthe seal with a source of pressurised fluid being provided at one end ofthe seal, and the other end of the seal being closed to prevent escapeof fluid therefrom.
 8. An inflatable seal system as claimed in claim 7,wherein the connector is removable so as to be available for reuse withanother length of seal.
 9. An inflatable seal system as claimed in claim8, wherein the connector is applied substantially axially of the seal.10. An inflatable seal system as claimed in claim 7, wherein theconnector is applied substantially axially of the seal.
 11. A method ofinstalling an inflatable seal comprising locating a longitudinallyextending seal along a longitudinally extending seal cavity, cutting theseal to an appropriate length, inserting into at one end of the seal, aconnector for communicating the seal with a source of pressurised fluid,and closing the other end of the seal to prevent escape of fluidtherefrom.
 12. A method as claimed in claim 1, which comprises insertingsaid seal into said seal cavity through a slot in the top thereof. 13.The method as claimed in claim 11, wherein said seal comprises aninflatable portion and an abutment portion for sealingly abuttingagainst an opposing surface and wherein the inflatable portion remainsin the seal cavity when the seal is deflated.
 14. The method as claimedin claim 13, wherein said seal further comprises an inwardly projectingmember projecting into the seal to prevent the abutment portion of theseal fully entering the seal cavity when the seal is deflated.
 15. Themethod as claimed in claim 14, wherein said member projects radiallyinwardly from a wall of the inflatable portion which is substantiallyopposite said abutment portion.
 16. The method as claimed in claim 13,wherein the inflatable portion and the abutment portion are formedintegrally with each other.
 17. The method as claimed in claim 13,wherein the seal is an extrusion.
 18. The method as claimed in claim 13,wherein the seal is not reinforced by a second material.
 19. The methodas claimed in claim 11, wherein the seal cavity is defined in a body ofmoulded material.
 20. An inflatable seal system produced by the methodof claim 11 and comprising a longitudinally extending seal cavity and aseal extending longitudinally along the seal cavity, the seal being cutto a length appropriate for the seal cavity, a connector forcommunicating the seal with a source of pressurized fluid being insertedin one end of the seal, and the other end of the seal being closed toprevent escape of fluid therefrom.
 21. A method of making a mouldedarticle comprising placing an article to be moulded between first andsecond mould parts, one of said first and second mould parts comprisingan inflatable seal system as claimed in claim 1, moving said first andsecond mould parts together, inflating said seal system, performing amoulding operation, deflating said inflatable seal system, moving saidfirst and second mould parts apart, and removing said moulded article.22. A method of making a moulded article comprising placing an articleto be moulded between first and second mould parts, one of said firstand second mould parts comprising an inflatable seal system as claimedin claim 20, moving said first and second mould parts together,inflating said seal system, performing a moulding operation, deflatingsaid inflatable seal system, moving said first and second mould partsapart, and removing said moulded article.